Because Azmath made omnitrix to stop the upcoming destruction of Ascalon and also for peace but the Ultimatrix is the reverse of omnitrix as it transform ben into the evolve form of an Alien which causes two major impact :- 1. Forcefully evolved and recreated DNA of aliens and added a personality (which we see in the series in the Ultimate Sacrifice episode 2. Causes ben and others life in danger as it supports most of the glitches. So that's why Azmath didnt like Ultimatrix or as such or Evolutionary function